A growing number of Alzheimer’s disease genes are linked to innate immunity and neuroinflammatory pathways. AD mouse models have been used to test the effects of these microglial genes on AD pathogenesis. However, it has not been possible to precisely test the impact of AD-associated microglial genetic variant due to fundamental differences in gene structures between human and mouse. Recently, we developed a three-dimensional human neuron-astrocyte-microglia triculture AD model, which recapitulates neuroinflammation in a human AD brain-like environment (Park et al., Nat. Neurosci. 2018). We demonstrate that human microglial cells are recruited toward 3D AD (amyloid beta-producing) neuron-astrocyte cultures via microglia-specific migration channels, in a chemokine-dependent manner, leading to neuroinflammation and neurodegeneration. In this project, we will explore the molecular mechanism underlining AD-associated neuroinflammation/neurodegeneration and the impact of AD-associated microglial genetic variants on AD pathology in the single cellular level by using single-cell RNAseq. In the previous period, we focused on developing a novel 3D-3D triculture model that does not require microfluidic devices. Compared with the published microfluidic semi 2D-3D triculture models, the 3D-3D model is advantageous for single-cell analysis and high-throughput drug screening. The new 3D-3D triculture models also provide a valid platform for studying human-induced pluripotent stem cell-derived microglial cells—male and female—with or without AD-associate genetic variants.
A growing number of Alzheimer’s disease (AD)-associated genes are linked to innate immunity and neuroinflammatory pathways. Microglial gene networks are strongly associated with AD neuropathology. Using whole-genome sequencing and whole-exome sequencing datasets have revealed variants in Alzheimer’s disease-associated microglial genes that include CD33, TREM2, PILRA/B, MS4A cluster, ABCA7 and CR1, to name a few. Whole-exome sequencing is a genetic technique for sequencing all of the protein-coding genes in a genome. Using these datasets as well as our novel human neuron-astrocyte-microglia triculture AD model referred to commonly as “Alzheimer’s in a Dish,” we will validate the effects of microglial AD-risk gene mutations and identify novel mechanisms of the disease related to innate immunity and neuroinflammation.